有條不紊的復(fù)習(xí)才能讓你更好的應(yīng)對考試。以下是出國留學(xué)網(wǎng)GMAT考試欄目為大家整理的2015年2月GMAT閱讀機(jī)經(jīng)，供大家參考!
2015年2月GMAT閱讀機(jī)經(jīng)——火山熔漿的形成
【V1】
(關(guān)鍵詞: Lava，melting, 希望對考古有幫助)
通篇反正就是在說科學(xué)家在研究火山熔漿形成的過程中發(fā)生了哪些化學(xué)反應(yīng)(有題問這文章主要講什么，選這個)，然后說了幾個實(shí)驗，具體內(nèi)容不記得，然后第二段說在海底發(fā)現(xiàn)的lava sample里面又出現(xiàn)了和第一段相反的情況，然后又說了對于這個情況的兩種解釋，第一種還是有問題，作者認(rèn)為第二種更靠譜，第二種有提到通過small channels之類的東西在什么之前就完成了化學(xué)反應(yīng)，之后就不會再有反應(yīng)了(這里有題)
【V2】
還有一篇是lava的，我找的13年7月的，我看到的和這個基本一致，這篇不長，1屏不到
P1講火山爆發(fā)來源于Mantle中的Lava，而Lava來源于Melt ，Melt在向地表上升的過程中會與Mantle中的Rock反應(yīng)并不斷互相交換物質(zhì)、變化結(jié)構(gòu)，即吸收Orthopyroxene并排出Olivine。越接近c(diǎn)loser表面surface，lava的exchange越頻繁
P2一個跟理論不太相符的事情，一種海底里的lava sample，在距離地表45千米突然發(fā)現(xiàn)已經(jīng)停止這種物質(zhì)交換，Melt的結(jié)構(gòu)不變了。一種假設(shè)是那里的Mantle太松散了，使Melt無法與他們接觸并交換物質(zhì)，但立即被否定了(因為45KM還很深東西都很軟，沒有裂縫)。另一種假設(shè)是Melt在之前的上升過程中已經(jīng)吸收了足夠的Orthopyroxene， 并將能排出的Olivine都排了，無法繼續(xù)反應(yīng)。
最后一篇我連一個關(guān)鍵詞都想不起來了，想要考古找內(nèi)容幫大家也不行啦，大家參考別的狗狗吧~
【考古】
V1 duke3d001 750, wade777, echosweet 700 & yueqianchen
關(guān)鍵詞：45KM, Olivine, Orthopyroxene (referenced by gitarrelieber)。這篇文章的題目不難，狗的骨架也很清晰。
第一段講火山爆發(fā)來源于Mantle中的Lava，而Lava來源于Melt ，Melt在向地表上升的過程中會與Mantle中的Rock反應(yīng)并不斷互相交換物質(zhì)、變化結(jié)構(gòu)，即吸收Orthopyroxene并排出Olivine。
第二段說一個跟理論不太相符的事情，一種海底里的lava sample，在距離地表45千米突然發(fā)現(xiàn)已經(jīng)停止這種物質(zhì)交換，Melt的結(jié)構(gòu)不變了。一種假設(shè)是那里的Mantle太松散了，使Melt無法與他們接觸并交換物質(zhì)，但立即被否定了(因為45KM還很深東西都很軟，沒有裂縫)。另一種假設(shè)是Melt在之前的上升過程中已經(jīng)吸收了足夠的Orthopyroxene， 并將能排出的Olivine都排了，無法繼續(xù)反應(yīng)。
1 darkchoco 710是什么可以證明這種exchange的存在：熔巖的成分
2 gyz12 740 一道文章最后句定位：Olivine的用完了,exchange就停止了
3 gyz12 740 一道是選chemical composition為特征 sashimiyuki 720 V37 選“lab experiments” indicate 那個melt 的變化的，沒有選chemical composition, 細(xì)節(jié)題定位后決定的，確認(rèn)后到現(xiàn)在還沒有深深后悔過
4 tianmo0512 是什么發(fā)生反應(yīng)：選melt
5 feifeizoe 750 V39 文中什么情況下描述了那種正常的exchange：lab experiment中實(shí)現(xiàn)了那種現(xiàn)象
6 The author mention “the melt to rise so rapidly” in order to：提出了一種hypothesis，這種hypothesis在后面被反駁
(疑似)原文未縮減 gitarrelieber (sereneys 730 V40 基本確認(rèn))
節(jié)選自The Origin of the Land under the Sea (Scientific American Magazine @ February 2009)
Author: Peter B. Kelemen
Knowledge of the intense heat and pressure in the mantle led researchers to hypothesize in the late 1960s that ocean crust originates as tiny amounts of liquid rock known as melt—almost as though the solid rocks were “sweating.” Even a minuscule release of pressure (because of material rising from its original position) causes melt to form in microscopic pores deep within the mantle rock. Explaining how the rock sweat gets to the surface was more difficult. Melt is less dense than the mantle rocks in which it forms, so it will constantly try to migrate upward, toward regions of lower pressure. But what laboratory experiments revealed about the chemical composition of melt did not seem to match up with the composition of rock samples collected from the mid-ocean ridges, where eruptedmelt hardens. Using specialized equipment to heat and squeeze crystals from mantle rocks in the laboratory, investigators learned that the chemical composition of melt in the mantle varies depending on the depth at which it forms; the composition is controlled by an exchange of atoms between the melt and the minerals that makeup the solid rock it passes through. The experiments revealed that as melt rises, it dissolves one kind of mineral, orthopyroxene, and precipitates, or leaves behind, another mineral, olivine. Researchers could thus infer that the higher in the mantle melt formed, the more orthopyroxene it would dissolve, and the more olivine it would leave behind.(melt上升時， 溶解Ort產(chǎn)生Oli, 所以melt higher， 溶解的Ort越多，產(chǎn)生的/留在身后的Oli也越多) Comparing these experimental findings with lava samples from the mid-ocean ridges revealed that almost all of them have the composition of melts that formed at depths greater than 45kilometers. This conclusion spurred a lively debate about how meltis able to rise through tens of kilometers of overlying rock while preserving the composition appropriate for a greater depth. If melt rose slowly in smallpores in the rock, as researchers suspected, it would be logical to assume that all melts would reflect the composition of the fashallowest part of the mantle,at 10 kilometers or less. Yet the composition of most mid-ocean ridge lavas amples suggests their source melt migrated through the uppermost 45 kilometers of the mantle without dissolving any orthopyroxene from the surrounding rock. But how? (疑大概為狗狗第一段的背景內(nèi)容)
In the early 1970s scientists proposed an answer: the melt must make the last leg of its upward journey along enormous cracks. Open cracks would allow the melt to rise so rapidly that it would not have time to interact with the surrounding rock, nor would melt in the core of the crack ever touch the sides. Although open cracks are not a natural feature of the upper mantle— the pressure is simply too great—some investigators suggested that the buoyant force of migrating melt might sometimes be enough to fracture the solid rock above, like an icebreaker ship forcing its way through polar pack ice. Adolphe Nicolas of the University of Montpellier in France and his colleagues discovered tantalizing evidence for such cracks while examining unusual rock formations called ophiolites. Typically, when oceanic crust gets old and cold, it becomes so dense that it sinks back into the mantle along deep trenches known as subduction zones, such as those that encircle the Pacific Ocean. Ophiolites, on the other hand, are thick sections of old seafloor and adjacent, underlying mantle that are thrust up onto continents when two of the planet’s tectonic plates collide. A famous example, located in the Sultanate of Oman, was exposed during the ongoing collision of the Arabian and Eurasian plates. In this and other ophiolites, Nicolas’s team found unusual, light-colored veins called dikes, which they interpreted as cracks in which melt had crystallized before reaching the seafloor. The problem with this interpretation was that the dikes are filled with rock that crystallized from a melt that formed in the uppermost reaches of the mantle, not below 45 kilometers, where most mid-ocean ridge lavas originate. In addition, the icebreaker scenario may not work well for the melting region under mid-ocean ridges: below about 10 kilometers, the hot mantle tends to flow like caramel left too long in the sun, rather than cracking easily.
To explain the ongoing mystery, I began working on an alternative hypothesis for lava transport in the melting region. In my dissertation in the late 1980s, I developed a chemical theory proposing that as rising melt dissolves orthopyroxene crystals, it precipitates a smaller amount of olivine, so that the net result is a greater volume of melt. Our calculations revealed how this dissolution process gradually enlarges the open spaces at the edges of solid crystals, creating larger pores and carving a more favorable pathway through which melt can flow. As the pores grow, they connect to form elongate channels. In turn, similar feedbacks drive the coalescence of several small tributaries to form larger channels. Indeed, our numerical models suggested that more than 90 percent of the melt is concentrated into less than 10 percent of the available area. That means millions of microscopic threads of flowing melt may eventually feed into only a few dozen, high porosity channels 100 meters or more wide. Even in the widest channels, many crystals of the original mantle rock remain intact, congesting the channels and inhibiting movement of the fluid. That is why melt flows slowly, at only a few centimeters a year. Over time, however, so much melt passes through the channels that all the soluble orthopyroxene crystals dissolve away, leaving only crystals of olivine and other minerals that the melt is unable to dissolve. As a result, the composition of the melt within such channels can no longer adjust to decreasing pressure and instead records the depth at which it last “saw” an orthopyroxene crystal. One of the most important implications of this process, called focused porous flow, is that only the melt at the edges of channels dissolves orthopyroxene from the surrounding rock; melt within the inner part of the conduit can rise unadulterated.
【考古2】
V1
第一段：說的是火山爆發(fā)中熔巖(lava)是來自地幔的(mantle)，說是由地下升起來的，在此過程中成分變化,一種物質(zhì)O1(O打頭)增加，另一個O2(也是O打頭)減少。
第二段：海底火山樣本大概都證明了，但是奇怪的是45KM時成分就不變了，這是怎么回事呢?若是不變它如何上來的呢?第一種解釋說是沿著裂縫上來的(crack)，然后說不可能啊，因為45KM還很深東西都很軟，沒有裂縫。第二種解釋又說，到45KM時O2就用完了 - 題目實(shí)在記不起來記得都挺好找的
V2
還有l(wèi)ava的那個
第一段是一個試驗說從mantle 怎樣就變成了melt 然后說越靠近surface越多 Ose。。很長一個單詞 然后越少 Olive之類的一個單詞。
第二段說在可是ocean land里面 45km以下就沒有這種substance的exchange 然后就分析原因 有一個是rock太軟不會裂開怎么流不出去還有幾個解釋忘記了
文言文 nowwsy & XYXB 未確認(rèn)
V1 bhj & parkmm V34 & zebracxy 730 V38 (Golden 綜合版)
是火山，說火山噴發(fā)，噴出來一種叫什么"mamgo"(M)的東西(不確定是不是這個詞)
地質(zhì)學(xué)家一直認(rèn)為M這個東西是在地底下很久了，這個東西一旦噴出來以后，更下面的這個東西會重新填滿噴出去的區(qū)域。但是有人站出來說這種觀點(diǎn)是不對的，因為如果是這樣，是不穩(wěn)定的，火山會繼續(xù)噴發(fā)。然后說，最近研究了一個在火山巖里面的一個晶體，叫"Zinroc"的東西(不確定是不是這個詞)。說這里面的氧的含量和在很深的地底下的M的含氧量是不一樣的。按照前面的假說，這兩個含氧量應(yīng)該是一樣的。而含氧量又和雨水里面的含氧量一致。所以說，那個M噴發(fā)出來以后是地表的石頭掉下去又形成的新的M。
1、主題題。
2、在很深的地底下的M會怎么樣。一個選項是說那些東西在那里幾百萬年了，還有一個選項說這個東西沒有那個Z什么的，還有一個選項說含氧量不一樣。我不確定答案。
3、地下的mamgo怎么了，答“叢地面陷下去的” (這題很sure)
4、知道第一次噴發(fā)的巖漿怎么樣，我選了含氧量不一樣，供參考!
希望以上《2015年2月GMAT閱讀機(jī)經(jīng)(火山熔漿的形成)》一文能給大家提供幫助!
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